U.S. patent application number 09/130151 was filed with the patent office on 2002-05-09 for gas-discharge display panel, a display using the same, and a method of manufacturing the same.
Invention is credited to IWANAGA, SHOICHI, KATO, YOSHIHIRO, KAWAI, MICHIFUMI, MOTOWAKI, SHIGEHISA, NAITO, YUTAKA, SATOH, RYOHEI, SUZUKI, KAZUO, SUZUKI, SHIGEAKI.
Application Number | 20020053876 09/130151 |
Document ID | / |
Family ID | 16655056 |
Filed Date | 2002-05-09 |
United States Patent
Application |
20020053876 |
Kind Code |
A1 |
KAWAI, MICHIFUMI ; et
al. |
May 9, 2002 |
GAS-DISCHARGE DISPLAY PANEL, A DISPLAY USING THE SAME, AND A METHOD
OF MANUFACTURING THE SAME
Abstract
A gas-discharge display panel is manufactured by sealing up a
front substrate and a rear substrate by a sealing member. A
relationship of Tg.gtoreq.Tf exists between a glass transition
point Tg of a dielectric substance formed on the front substrate
and a temperature Tf at which the front substrate and the rear
substrate are sealed up.
Inventors: |
KAWAI, MICHIFUMI; (TOKYO,
JP) ; SATOH, RYOHEI; (YOKOHAMA-SHI, JP) ;
IWANAGA, SHOICHI; (YOKOHAMA-SHI, JP) ; SUZUKI,
SHIGEAKI; (FUJISAWA-SHI, JP) ; SUZUKI, KAZUO;
(YOKOHAMA-SHI, JP) ; MOTOWAKI, SHIGEHISA;
(YOKOHAMA-SHI, JP) ; KATO, YOSHIHIRO;
(YOKOHAMA-SHI, JP) ; NAITO, YUTAKA; (TOKYO,
JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT & KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
16655056 |
Appl. No.: |
09/130151 |
Filed: |
August 6, 1998 |
Current U.S.
Class: |
313/587 |
Current CPC
Class: |
H01J 11/12 20130101;
H01J 9/261 20130101; H01J 11/48 20130101; H01J 11/38 20130101 |
Class at
Publication: |
313/587 |
International
Class: |
H01J 017/49 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 1997 |
JP |
09-214393 |
Claims
1. A gas-discharge display panel, comprising: a front substrate;
and a rear substrate to be sealed up with the front substrate by a
sealing member, wherein a relationship of Tg.gtoreq.Tf exists
between a glass transition point Tg of a dielectric substance
formed on the front substrate and a temperature Tf at which the
front substrate and the rear substrate are sealed up.
2. A display, comprising: a gas-discharge display panel including a
front substrate and a rear substrate; and a driving circuit for
supplying a driving waveform to the display panel, wherein a
relationship of Tg.gtoreq.Tf exists between a glass transition
point Tg of a dielectric substance formed on the front substrate
and a temperature Tf at which the front substrate and the rear
substrate are sealed up.
3. A gas-discharge display panel, comprising: a front substrate; a
rear substrate to be sealed up with the front substrate by a
sealing member; a dielectric substance formed on the front
substrate; and a protective layer formed on the dielectric
substance through a heating process, wherein a relationship of
Tg.gtoreq.(Tf-20.degree. C.) exists between a glass transition
point Tg of the dielectric substance formed on the front substrate
and a temperature Tf at which the front substrate and the rear
substrate are sealed up.
4. A display, comprising: a gas-discharge display panel including a
front substrate and a rear substrate; a driving circuit for
supplying a driving waveform to the display panel; a dielectric
substance formed on the front substrate; and a protective layer
formed through a heating step on the dielectric substance, wherein
a relationship of Tg.gtoreq.(Tf-20.degree. C.) exists between a
glass transition point Tg of the dielectric substance formed on the
front substrate and a temperature Tf at which the front substrate
and the rear substrate are sealed up.
5. A gas-discharge display panel, comprising: a front substrate;
and a rear substrate to be sealed up with the front substrate by a
sealing member, wherein the sealing member includes a crystallizing
material.
6. A gas-discharge display panel in accordance with claim 5,
wherein the sealing member includes a material substantially
crystallizing in the sealing step.
7. A display, comprising: a gas-discharge display panel including a
front substrate and a rear substrate; and a driving circuit for
supplying a driving waveform to the display panel, wherein the
sealing member includes a crystallizing material.
8. A display in accordance with claim 7, wherein the sealing member
includes a material substantially crystallizing in the sealing
step.
9. A method of manufacturing a gas-discharge display panel,
comprising the steps of: forming transparent electrodes and first
electrodes on a front substrate; forming a thick dielectric layer
with a dielectric substance having a glass transition point of Tg
on the front substrate, the layer covering substantially the
overall surface of the transparent and first electrodes; forming a
protective layer on the thick dielectric layer, the layer emitting
secondary electrons; forming second electrodes on a rear substrate;
forming a thick dielectric layer with a dielectric substance having
a glass transition point of Tg on the rear substrate and the second
electrodes; aligning the front substrate onto the rear substrate
and sealing up the front and rear substrates by a sealing agent at
a sealing temperature of Tf (Tf.ltoreq.Tg); and exhausting air from
a space formed by sealing up the front substrate and the rear
substrate to a vacuum and introducing a discharge gas into the
space.
10. A method of manufacturing a gas-discharge display panel,
comprising the steps of: forming transparent electrodes and first
electrodes on a front substrate; forming a thick dielectric layer
with a dielectric substance having a glass transition point of Tg
on the front substrate, the layer covering substantially the
overall surface of the transparent and first electrodes; forming a
protective layer on the thick dielectric layer, the layer emitting
secondary electrons; forming second electrodes on a rear substrate;
forming a thick dielectric layer with a dielectric substance having
a glass transition point of Tg on the rear substrate and the second
electrodes; aligning the front substrate onto the rear substrate
and sealing up the front and rear substrates by a sealing agent at
a sealing temperature of Tf (Tf.ltoreq.Tg+20.degree. C.); and
exhausting air from a space formed by sealing up the front
substrate and the rear substrate to a vacuum and introducing a
discharge gas into the space.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a gas-discharge display
panel such as a plasma display panel and a display using the
same.
[0002] Since the gas-discharge display panel such as a plasma
display panel achieves a display operation through a self-emission,
there are obtained a large angle of visual field and improved
visibleness of displayed images. Moreover, the gas-discharge
displays have the following aspects, for example, it is possible to
produce a display with a reduced thickness and there can be
fabricated a large-sized screen, and hence gas-discharge displays
have already been put to use for information terminal facilities
and high-definition television sets. The plasma displays can be
fundamentally classified into a direct-current (dc) type and an
alternate-current (ac) type. Of these types of displays, the ac
plasma displays have a high luminance thanks to a memory action of
a dielectric layer coating electrodes, and there can be obtained a
life for practices owing to the formation of protective layers. As
a result, the plasma display is practically adopted as a
multipurpose video monitor.
[0003] FIG. 4 is a perspective view showing constitution of a
plasma display panel practically used. In this diagram, a front
substrate 100 is apart from a rear substrate 200 and a discharging
region 300 for easy understanding of the constitution.
[0004] In the constitution, the front substrate 100 includes a
front glass substrate 400 on which display electrodes 600 including
a transparent conductive material such as indium tin oxide (ITO)
and tin oxide (SnO.sub.2), bus electrodes 700 including a
low-resistance material, a dielectric layer 800 including a
transparent insulating material, and a protective layer 900
including magnesium oxide (MgO) are fabricated.
[0005] The rear substrate 200 includes address electrodes 100,
barrier ribs 1100, and a fluorescent layer 1200 on a rear glass
substrate 500. Additionally, although not shown, a dielectric layer
1300 is also formed on the address electrodes 1000.
[0006] Moreover, the front substrate 100 is fixed onto the rear
substrate 200 such that the display electrodes (transparent
electrodes) 600 are orthogonal to the address electrodes 1000,
which forms the discharging region 300 between the front substrate
100 and the rear substrate 200.
[0007] In addition, although not shown, to fill a discharge gas
into a space between the front substrate 100 and the rear substrate
200, the construction includes peripheral portions sealed with a
sealing member including a glass material.
[0008] In this gas-discharge display, when an ac voltage is applied
between a pair of display electrodes 600 disposed on the front
substrate 100 and a voltage is applied between the address
electrode 1000 and the display electrode 600, there takes place an
address discharge to lead to a main discharge in a predetermined
discharge cell. Using an ultraviolet ray generated by the main
discharge, fluorescent substances 1200 of red, green, and blue
respectively painted on the respective discharge cells emit lights
so as to conduct the display operation. Respective voltages are
applied to the respective electrodes by a driving circuit not show
in the drawings.
[0009] A conventional example of the gas-discharge display shown
above has been described in pages 208 to 215 of the "Flat Panel
Display 1996" published from Nikkei Micro-Device in 1995.
SUMMARY OF THE INVENTION
[0010] It is therefore an object of the present invention to
provide a gas-discharge display panel having a high picture quality
capable of preventing occurrence of cracks in a protective layer
which has a high secondary-electron emission characteristic and
which is disposed on a dielectric layer.
[0011] Another object of the present invention is to provide a
gas-discharge display panel in which a sealing material has high
reliability in a high-temperature process to thereby produce
high-quality pictures.
[0012] In the plasma display panel of this kind, there is included
the protecting layer 900 of MgO or the like having a high value of
the secondary electron emission characteristic for the emission of
light from the fluorescent substance 1200. There arises a great
problem of cracks in the protecting layer 900. When cracks appear
in the protecting layer 900, the quality of picture itself is
deteriorated.
[0013] A first problem to be solved by the present invention is how
to prevent cracks from appearing in the thin MgO film on the
dielectric layer.
[0014] On the other hand, in the configuration of the conventional
plasma display panel, the front substrate 100 and the rear
substrate 200 are sealed up. In some cases, the sealed panel is
treated at a high temperature to activate the protecting layer 900
of MgO. In this case, although it is desired to activate the
protecting layer 900 of MgO at a possibly high temperature, the
temperature is limited to the temperature at which the front
substrate 100 and the rear substrate 200 are sealed up. This is
because of a fear that when the activation process is accomplished
at a temperature exceeding the sealing temperature, the sealing
material is softened and hence the joining strength is deteriorated
between the front substrate 100 and the rear substrate 200 and the
sealed discharge gas such as a rare gas leaks therefrom.
[0015] A second problem to be solved by the present invention is
how to increase reliability of the sealing material in the
high-temperature process.
[0016] Through discussion on the cause of occurrence of cracks in
the thin MgO film, it has been known that the occurrence of cracks
is closely related to the temperature Tf at which the front
substrate 100 and the rear substrate 200 are sealed up with the
sealing material. That is, the thin MgO film is formed on the
dielectric substance fabricated in a thick-film process in which
there exists a difference in thermal expansion between the
dielectric layer and the thin MgO film. Consequently, these
substances respectively thermally expand and the difference in
thermal expansion leads to the cracks.
[0017] FIG. 5 shows a relationship between temperature and thermal
expansion for the dielectric material and MgO. As can be seen from
this graph, the thermal expansion almost linearly increases with
respect to temperature. However, the dielectric material generally
employed in the plasma display panels is a glass substance and
hence the thermal expansion thereof abruptly increases when the
temperature exceeds a certain value. The temperature is generally
called a glass transition point Tg. Details about the glass
transition point has been described in pages 119 and 120 of the
"Garasu No Kagaku or Chemistry of Glass (1st edition published on
24 Apr., 1972).
[0018] In consequence, when the sealing temperature Tf is equal to
or more than the glass transition point Tg unique to the dielectric
material utilized for the dielectric layer, the difference in
thermal expansion between the dielectric layer and MgO becomes
larger and hence there appear cracks in proportion to the
temperature difference.
[0019] In this situation, to achieve the first object above, there
is provided in accordance with the present invention a
gas-discharge display panel including a front substrate and a rear
substrate which are sealed up by a sealing member. In the display
panel, there exists a relation of Tg.gtoreq.Tf between a glass
transition point Tg of a dielectric substance formed on the front
substrate and a temperature Tf at which the front substrate and the
rear substrate are sealed up.
[0020] Additionally, there is provided a display including a
gas-discharge display panel including a front substrate and a rear
substrate and a driving circuit for supplying a driving waveform to
the display panel in which a relationship of Tg.gtoreq.Tf exists
between a glass transition point Tg of a dielectric substance
formed on the front substrate and a temperature Tf at which the
front substrate and the rear substrate are sealed up.
[0021] Since the sealing is conducted at a temperature equal to or
less than the glass transition point of the dielectric substance,
the ratio of expansion of the dielectric layer becomes almost equal
to that of the MgO film (i.e., does not abruptly increases), which
can prevent the occurrence of cracks in the MgO film due to the
expansion difference between the dielectric layer and the MgO film.
Additionally, since the cracks occurring in the MgO film can be
suppressed, the picture quality is retained.
[0022] In this connection, the protecting layer of the MgO film or
the like is desirably produced through vacuum evaporation at a film
forming temperature from about 250.degree. C. to about 300.degree.
C. The MgO film grown under this condition is in a state in which a
compressive stress appears in the cooling process thereof. It has
been consequently known through experiments that in the MgO film
grown at such a temperature, expansion of the dielectric layer can
be suppressed in the sealing step thanks to the compressive stress
existing therein. Results of experiments will be described
later.
[0023] That is, in order to achieve the first object in accordance
with the present invention, there is provided a gas-discharge
display panel including a front substrate and a rear substrate
which are sealed up by a sealing member, comprising a dielectric
substance formed on the front substrate and a protective layer
formed through a heating step on the dielectric substance. In the
display panel, there exists a relationship of
Tg.gtoreq.(Tf-20.degree. C.) between a glass transition point Tg of
a dielectric substance formed on the front substrate and a
temperature Tf at which the front substrate and the rear substrate
are sealed up.
[0024] Alternatively, there is provided a display including a
gas-discharge display panel including a front substrate and a rear
substrate and a driving circuit for supplying a driving waveform to
the display panel in which the front substrate includes a
dielectric substance and a protective layer formed through a
heating step on the dielectric substance and a relationship of
Tg.gtoreq.Tf-20.degree. C.) exists between a glass transition point
Tg of a dielectric substance formed on the front substrate and a
temperature Tf at which the front substrate and the rear substrate
are sealed up.
[0025] Incidentally, in either cases, the difference in expansion
can be favorably removed in the sealing step by equalizing the
thermal expansion coefficient of MgO to that of the dielectric
material up to the glass transition point.
[0026] On the other hand, we have proved that a crystallizing
material is required to be used as the sealing material to improve
reliability of the sealing material in the high-temperature
process.
[0027] Namely, in order to achieve the second object in accordance
with the present invention, there is provided a gas-discharge
display panel including a front substrate and a rear substrate
which are sealed up by a sealing member, the sealing member
including a crystallizing material.
[0028] Alternatively, there is provided a display including a
gas-discharge display panel including a front substrate and a rear
substrate and a driving circuit for supplying a driving waveform to
the display panel, the sealing member including a crystallizing
material.
[0029] In this case, it is favorable to utilize as the sealing
member a material substantially crystallizing in the sealing
step.
[0030] FIG. 6 shows a viscosity characteristic .eta. for amorphous
and crystallizing materials with respect to temperature.
[0031] As can be seen from the graph, even after the sealing step
is completed, the amorphous material has a trend of softening with
respect to the increase in temperature.
[0032] In contrast therewith, when the sealing step is carried out
at a predetermined temperature, the crystallization continuously
takes place in the crystallizing material until the crystallization
is finally completed. Therefore, the characteristic of the
crystallizing material up to the end of sealing step considerably
differs from that after thereafter. It is consequently quite
difficult to soften the crystallizing material, namely, the
characteristic becomes almost fixed when compared with the
crystallizing material before the end of sealing step.
[0033] Consequently, in a case in which the crystallizing material
is used as the sealing material, when the sealing step is conducted
at a temperature satisfying the first object, the crystallized
sealing material is not easily softened even if an activation
process is accomplished for the material at a temperature equal to
or more than the sealing temperature. In consequence, it is
possible to prevent the deterioration in strength of joint between
the front substrate 100 and the rear substrate 200 and hence the
leakage of the sealed discharge gas such as a rare gas is
prevented. In other words, it is possible to improve the
reliability in the high-temperature process when compared with the
conventional technology.
[0034] As above, in accordance with the present invention, the
decrease in the insulating voltage of the dielectric substance and
the cracks in the MgO film are prevented and hence there can be
provided a gas-discharge display panel and a display using the same
capable of displaying a high-quality picture.
[0035] In addition, in accordance with the present invention, it is
possible to improve reliability of the sealing material in the
high-temperature process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The objects and features of the present invention will
become more apparent from the consideration of the following
detailed description taken in conjunction with the accompanying
drawings in which:
[0037] FIG. 1 is a cross-directional view showing an embodiment in
accordance with the present invention;
[0038] FIG. 2 is a table showing results of experiments in
accordance with the present invention;
[0039] FIG. 3 is a table showing results of experiments in
accordance with the present invention;
[0040] FIG. 4 is a cross-directional view showing an example of the
prior art;
[0041] FIG. 5 is a graph showing the principle of the present
invention;
[0042] FIG. 6 is a graph showing the principle of the present
invention;
[0043] FIG. 7 is a photo showing presence or absence of occurrence
of cracks;
[0044] FIG. 8 is a photo showing presence or absence of occurrence
of cracks;
[0045] FIG. 9 is a photo showing presence or absence of occurrence
of cracks; and
[0046] FIG. 10 is a photo showing presence or absence of occurrence
of cracks.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0047] Next, description will be given in detail of an embodiment
in accordance with the present invention by referring to the
accompanying drawings.
[0048] FIG. 1 shows constitution of a plasma display panel and an
example of process of manufacturing the panel.
[0049] This diagram includes a front substrate 1, a rear substrate
2, transparent electrodes 3 formed on the substrate 1, metal
electrodes 4 formed on the transparent electrodes 3, metal
electrodes 5 formed on the rear substrate 2, thick dielectric
layers 6 and 7 formed to respectively coat the transparent
electrodes 3 and the metal electrodes 4 and 5, an MgO film 8, and a
sealing member 9.
[0050] First, the transparent electrodes 3 and the metal electrodes
4 are manufactured on the front substrate 1 in photolithography and
etching steps. Subsequently, the thick dielectric layer 6 is
fabricated to almost entirely coat the transparent electrodes 3 and
the metal electrodes 4. Thereafter, the MgO film 8 is formed in a
vacuum on the fabricated dielectric layer 6. The MgO film 8 is
fabricated entirely on the surface of the dielectric layer 6 with a
small peripheral region left on the surface.
[0051] Similarly, the metal electrodes 5 and the thick dielectric
layer 7 are fabricated on the rear substrate 2. Thereafter,
isolating walls 10 are formed in the sand-blast process or the like
and a fluorescent substance 11 is coated thereon.
[0052] The front substrate 1 and the rear substrate 2 manufactured
as above are aligned to each other and the peripheral sections
thereof are sealed up by the sealing member 9 as shown in the
diagram. For example, an amorphous or crystallizing lead glass is
generally adopted as the sealing material 9. Alternatively, there
may also be used a vanadium glass depending on cases. Although not
shown, after exhausting air of the internal space of the panel
through a hole prepared in the rear substrate 2 to establish a
vacuum state therein, the discharge gas such as a rare gas is
introduced into the space to thereby produce the completed plasma
display panel.
[0053] FIGS. 2 and 3 show relationships (results of experiments)
between the glass transition point Tg (350.degree.
C..ltoreq.Tg.ltoreq.480.degree- . C.) of the dielectric material as
the thick dielectric layer 6 and the sealing temperature
(400.degree. C..ltoreq.Tf.ltoreq.450.degree. C.) in the plasma
display panel constructed as above. A lead borosilicate dielectric
substance is employed as the thick dielectric layer 6. In this
connection, FIGS. 2 and 3 are experimental results respectively
obtained when the MgO is fabricated at a room temperature and at a
temperature of about 250.degree. C., respectively. It is also
possible to use a vanadium glass as the dielectric material of the
dielectric layer 6.
[0054] As can be seen from FIGS. 2 and 3, there appears no crack
when Tg.gtoreq.Tf is satisfied for the MgO film grown at a room
temperature and Tg.gtoreq.(Tf-20.degree. C.) is satisfied for the
MgO film grown at 250.degree. C.
[0055] That is, it is to be appreciated that the thermal expansion
of the thick dielectric layer becomes approximately equal to that
of the MgO film when the conditions above are satisfied (i.e., the
thick dielectric layer is within the glass transition point and
hence the abrupt thermal expansion thereof is suppressed) and
consequently no crack appears in the MgO film. Additionally, it can
also be confirmed that when the MgO film is grown at about
250.degree. C., the compressive stress resultantly occurring
therein develops an effect to suppress cracks.
[0056] FIGS. 7 to 10 are photos showing presence or absence of
occurrence of cracks in samples shown in FIG. 3.
[0057] FIG. 7 related to a case in which sample 10 (softening point
400.degree. C.) is sealed at about 430.degree. C. shows occurrence
of cracks.
[0058] FIG. 8 associated with a case in which sample 10 (softening
point 400.degree. C.) is sealed at about 410.degree. C. shows no
crack.
[0059] FIG. 9 associated with a case in which sample 7 (softening
point 415.degree. C.) is sealed at about 430.degree. C. shows no
crack.
[0060] FIG. 10 associated with a case in which sample 7 (softening
point 415.degree. C.) is sealed at about 410.degree. C. shows no
crack.
[0061] In accordance with the results of experiments, it is known
that no crack takes place when Tg.gtoreq.(Tf-20.degree. C.) is
satisfied.
[0062] In the embodiment, description has been given of results of
experiments in which the MgO film is grown at about 250.degree. C.
This is substantially an upper-limit film growing condition derived
from a relationship between the volume of gas generated in the
high-temperature process and influence thereof onto the vacuum.
However, the present invention is not to be restricted by this
example.
[0063] Moreover, it is to be appreciated that even if the
protective layer is fabricated with a material other than MgO,
almost the same effect can be obtained when there is employed a
material which has a high secondary-electron emission
characteristic and which is quite resistive against sputtering in
accordance with the principle of the present invention.
[0064] Additionally, even when a thin insulating inorganic film is
formed between the thick dielectric layer and the MgO film, it is
possible to prevent cracks which may be caused by the difference in
thermal expansion between the thick dielectric layer and the thin
insulating inorganic film as well as between the thick dielectric
layer and the MgO film.
[0065] Furthermore, the structure of the front substrate and the
rear substrate and the contour of the isolating wall are not
restricted by the example above. For example, even when the
isolating wall has a contour of a box or the isolating wall is
formed on the front substrate, the similar effect is obtainable.
Namely, the advantageous effect of the present invention is
obtainable by utilizing materials satisfying the relationship
between Tg and Tf in accordance with the present invention.
[0066] While the present invention has been described with
reference to the particular illustrative embodiments, it is not to
be restricted by those embodiments but only by the appended claims.
it is to be appreciated that those skilled in the art can change or
modify the embodiments without departing from the scope and spirit
of the present invention.
* * * * *